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A practical-scale cell (0.8 m 2 ) with a trickle-bed electrode was developed for on-site electrochemical production of hydrogen peroxide by the cathodic reduction of oxygen. Terminal voltage and current efficiency were affected by the dispersions of liquid and oxygen gas in the trickle-bed cathode and by the current density. Current efficiency was improved by obtaining uniform dispersions of electrolyte and oxygen in the trickle-bed cathode. A current efficiency of 97.4% was obtained at a cell voltage of 2.1 V and a current density of 1500 A m Ϫ2 . To save power, the temperature of the electrolyte was not controlled, and exothermic reactions increased the temperature of the anolyte recovered at the outlet from the inlet temperature of 37-44ЊC. The temperature of the catholyte rose simultaneously from an inlet temperature of 25-44ЊC. The crystallization of sodium peroxide within the cathodes was prevented by controlling peroxide concentration, and the maximum concentration of hydrogen peroxide in a 5.0% caustic soda solution was 2.1%.

We doped Vulcan XC-72 ͑VXC-72͒ with nitrogen by heating it under flowing NH 3 gas in various conditions and investigated its oxygen reduction reaction ͑ORR͒ activity in 0.1 M H 2 SO 4 . The cyclic voltammograms, X-ray photoelectron spectra, and Brunauer-Emmett-Teller analyses indicated that the heating temperature greatly influenced ORR activity, nitrogen content, and surface area of VXC-72. Furthermore, the heating time also influenced the ORR activity. Therefore, the rate of cooling as well as that of heating at above 773 K was found to be fixed to evaluate ORR activity. Under controlled heating/cooling conditions, the maximum onset potential for ORR was 0.70 V vs normal hydrogen electrode when VXC-72 was heated at 1223 K for 24 h under NH 3 gas ͑200 mL min −1 ͒.